Switchable component for a valve drive of an internal combustion engine

ABSTRACT

A switchable component, which has a housing with a bore and an inner element held in the bore with a head that projects above a rim of the housing. The housing and the inner element are loaded away from each other by a lost-motion spring. At least one coupling piston sits in an opening of the inner element. Sections of the coupling piston are moveable over a ring surface to a carrier surface of the housing. A retaining ring packet has a circular arc-shaped outer surface that lies in a ring groove of the bore of the housing. A ring face of the inner element sits against the underside of the retaining ring packet in the extended state defining relative position. The retaining ring packet, starting from at least one of the surfaces of the retaining ring packet has recesses for forming tab-like sections lying circumferentially between the recesses.

FIELD OF THE INVENTION

Switchable component for a valve drive of an internal combustion engine, in particular tappet or support element, having a housing, in the bore of which is held an inner element whose head is situated in the region of or projects beyond an edge of the housing, the elements being forced axially away from one another by a lost motion spring braced between them, and at least one coupling piston being seated in a cutout of one of the elements, which at least one coupling piston, in an axially remote relative position of the elements, can be moved beyond an annular surface between said elements and in sections into a driver surface of the in each case other element, a locking ring or a locking ring pack with a circular-arc-shaped outer shell resting in an annular groove of the bore of the housing, against the underside of which locking ring or locking ring pack the inner element, in the deployed state, bears with an annular face such that the relative position is defined.

BACKGROUND OF THE INVENTION

Already known from the prior art are switchable components such as roller tappets or support elements in which one locking ring or two locking rings situated one on top of the other are snapped into an annular groove of the housing thereof. The axially relatively movable inner element bears with an annular step or an annular face against an underside of said locking rings. This serves to provide primarily a height stop for the inner element in its deployed position, such that the at least one coupling piston in the inner element is in alignment with the driver surface thereof in the housing.

Furthermore, by means of locking rings provided in an assortment of thicknesses, it is also possible to set the coupling play (minimum required idle travel set (optimally) the same over a wide series of similar components, which travel is covered by the coupling means in the deployed position and, during a cam stroke, until the driver surface thereof is directly reached). In this regard, reference is made at this juncture to documents U.S. Pat. No. 6,321,704 (see FIGS. 2, 3) and DE 102 04 672. Use is conventionally made here of standardized or similar locking rings for bores which, according to the principle of “bending beams,” have an increasing width proceeding from the annular lugs thereof, which width is at its greatest in a region situated opposite the annular lugs. Said increase in width is realized at the inner shell of the locking rings.

A disadvantage of the abovementioned embodiments is that, in the case of a height stop against the underside of the corresponding locking ring, on account of the increasing width thereof, only an insufficiently large “sickle-shaped” contact surface is available for the inner element. It has also been found that the use of the abovementioned locking rings is problematic in particular in the case of very small component diameters. Here, plastic deformations or generally undesired excessive stresses may occur in the ring material when the ring is bent together during assembly.

OBJECT OF THE INVENTION

The invention is based on the object of providing a component of the abovementioned type in which the stated disadvantages are eliminated.

ACHIEVEMENT OF THE OBJECT

According to the invention, said object is achieved in that the locking ring/locking ring pack, proceeding from at least one of its shell surfaces [outer shell/inner shell], is formed with recesses so as to form lobe-like portions situated circumferentially in between.

A component is therefore provided in which the disadvantages cited in the introduction are eliminated. The at least one locking ring should serve primarily as a height stop for the inner element. It is however also preferable for the one or more locking rings to be provided in an assortment of thicknesses in the assembly facility, such that the required coupling play can be set in the same way by means of these.

It is also provided in a particularly expedient variant of the invention that, by means of the at least one locking ring, the inner element is likewise prevented from rotating relative to the housing by means of flattenings which communicate with one another.

On account of the proposed recesses which, in a physical embodiment of the invention, provide the respective locking ring with for example a wave-like or box-like profile on its corresponding shell surface, a variant is provided which is particularly well optimized with regard to stresses. Here, bending stresses which occur, in particular during assembly (bending-together and subsequent snapping into the annular groove of the bore of the housing), are no longer distributed uniformly over a distance according to the “bending beam” principle, but rather are distributed between discrete zones according to the “flexible pipe” principle. At the same time, the inner element, when in contact with the corresponding locking ring, is provided with an adequately large surface, such that the tilting tendency of said inner element, or the contact pressure in said region, is considerably reduced.

It has also been found that, when using the at least one locking ring, the assembly forces thereof can be kept well within limits, and plastic deformation of the locking ring in particular in the case of very small component diameters no longer occurs.

With the integration of the proposed rotation prevention surface, it is possible to dispense with complex separate rotation prevention measures such as those which involve pins pressed into the housing, or the like.

The at least one locking ring having the recesses according to the invention may have a constant width. Said at least one locking ring may however also be designed so as to have for example a greatest width at its section situated opposite the annular lugs, and a smallest (average) width in the section of the annular lugs.

A person skilled in the art will at this juncture recognize a multiplicity of possible designs of the shell surfaces of the corresponding locking ring. It is of importance at this juncture merely that the bending stress is well distributed between discrete zones.

If, as is proposed in one refinement of the invention, a rotation prevention means is realized by means of a flattening which projects in radially from the inner shell of the corresponding locking ring, then it is particularly expedient for the annular lugs of the corresponding locking ring to project radially outward into an aperture of the housing and to be fixed there, by means of the outer sides thereof, on respective inner sides of the aperture. Any occurring torque can be well absorbed in this way.

In a further refinement of the invention, it is proposed that the annular groove of the bore of the housing for holding the at least one locking ring be formed directly in the region of the edge of the housing. Assembly “from above” is made particularly easy in this way. It is however also conceivable, and provided, for the annular groove to be arranged at some other height section of the bore of the housing. If appropriate, the at least one locking ring may also run on the outer shell of the inner element and communicate with a corresponding stop surface on the housing. Such a design is expressly encompassed by the scope of protection of the invention.

It is finally proposed that two diametrically opposite coupling pistons be positioned in the radial bore of the inner element, which coupling pistons, in the coupled state, can be moved into a driver surface, formed for example as a window, bore, annular groove or annular groove segment, in the housing. The respective piston may be flattened in sections proceeding from its radially outer face, at its “coupling side”. It is however also conceivable, and provided, for the coupling piston to be cylindrical.

As a switchable component having the measures according to the invention, consideration is given in particular, but not exclusively, to a switchable support element or a switchable roller tappet or mushroom-shaped tappet. The switchable component should preferably be provided with a hydraulic play compensating device.

It is therefore possible by means of the at least one locking ring according to the invention a) to form only a height stop, b) to realize a height stop and set a coupling play, c) to realize a height stop and a rotation prevention means, d) to provide only a rotation prevention means or e) to realize a height stop and provide a rotation prevention means and at the same time set the coupling play. Here, it is clear that the “setting the coupling play” variant preferably encompasses the height stop.

BRIEF DESCRIPTION OF THE DRAWING

The invention will expediently be explained in more detail on the basis of the drawing, in which:

FIG. 1 shows a component, designed as a support element, in longitudinal section with two coupling pistons;

FIG. 2 shows the component according to FIG. 1, but rotated by 90°; and

FIGS. 3 to 8 show cross-sections through the component in the section of the locking rings.

DETAILED DESCRIPTION OF THE DRAWING

FIGS. 1, 2 disclose a switchable component 1 designed as a support element. Said component is composed of a pot-shaped housing 2, in the bore 3 of which an inner element 4 is held in an axially movable manner. The latter projects with its head 5 beyond an edge 6 of the housing 2. A rocker arm may be supported at one end on said head 5.

The inner element 4 has, in its lower section, a cutout 8 formed as a radial bore. Two radially outwardly spring-loaded coupling pistons 9 are situated diametrically oppositely in said cutout 8, wherein a coupled state is illustrated here. The respective coupling piston 9 engages with its counterpart surface 29, which is formed on the underside of said coupling piston and is flat in sections, into a driver surface 11, which is designed as a window, in the housing 2, and said coupling piston thereby crosses an annular surface 10 between the housing 2 and the inner element 4.

A lost motion spring 7 is installed, in a manner known per se, between an underside of the inner element 4 and a base of the housing 2. Said lost motion spring 7 forces the inner element 4 axially out of the housing 2.

As can also be seen from FIGS. 1, 2, the bore 3 of the housing 2 has, close to the edge 6 thereof, an annular groove 12. A locking ring pack 13 comprising two locking rings situated one on top of the other runs in said annular groove. The locking ring pack 13 projects radially inward slightly beyond the annular surface 10 between the components 2, 4. The inner element 4 abuts with an annular face 16 against an underside 15 of the locking ring pack 13. A coupling position of the coupling piston 9 as illustrated is thereby provided. At the same time, in the case of said variant, the coupling play is “precisely set” (see DE 102 04 672 cited in the introduction) by means of locking rings 13 provided in an assortment of thicknesses (lower locking rings of uniform thicknesses, and upper locking rings in a variety of thicknesses). Also, coupling pistons 9 may be provided in an assortment of thicknesses as an alternative to or in combination with locking rings 13 in an assortment of thicknesses.

As can be seen from FIG. 2, the inner element 4 has a longitudinal flattening 21 on the outer shell 22 at a section which intersects the edge 6 of the housing 2. A bowstring-like flattening 20 (see also FIGS. 3 to 8) which projects radially inward from the inner shell 16 a of the respective locking ring 13 communicates with said longitudinal flattening. Annular lugs 17, 18 of the locking ring 13, which annular lugs are situated diametrically opposite the longitudinal flattening 21, project radially outward and project into an aperture 23 of the housing 2 (see FIG. 4). Said annular lugs bear with their outer sides 25, 26 against upright face walls 27, 28 of the aperture 23 and are excellent at supporting any torque. A simply-designed means for preventing the inner element 4 from rotating relative to the housing 2 is therefore formed, and it is possible to dispense with separate measures, as discussed in the introductory part of the description.

The explanations below relate to the specific design of the at least one locking ring 13. Here, the locking ring 13 has a constant outer diameter (envelope circle A), in the style of standardized locking rings for bores. Recesses 16 b are formed on the outer shell 14 and/or on the inner shell 16 a of the locking ring 13 so as to form lobe-like sections 16 c situated circumferentially in between. The locking ring 13 has a wave-like profile in FIG. 3, a grooved profile in FIG. 4, a tooth-like or box-like profile in FIGS. 5, 6, and a wave-like profile again in FIGS. 7, 8.

On account of the design according to the invention of the at least one locking ring 13, the bending stresses during assembly, in particular in the case of very small bore diameters, are considerably minimized in relation to previous solutions, and the risk of plastic deformation of the locking ring 13 is reduced or eliminated.

It has also been found that, on account of the measures according to the invention, the inner element 4, when in contact by means of its annular face 16 with an underside 15 of the locking ring pack 13, has an excellently-designed contact surface such that the component loading and tilting tendency of the inner element 4 are reduced.

List of Reference Numerals and Symbols  1 Component  2 Housing  3 Bore  4 Inner Element  5 Head  6 Edge  7 Lost Motion Spring  8 Cutout  9 Coupling Piston 10 Annular Surface 11 Driver Surface 12 Annular Groove 13 Locking Ring, Locking Ring Pack 14 Outer Shell 15 Underside 16 Annular Face 16a) Inner Shell 16b) Recess 16c) Section 17 Annular Lug 18 Annular Lug 19 Section 20 Flattening 21 Longitudinal Flattening 22 Outer Shell Surface 23 Aperture 24 Not Assigned 25 Outer Side 26 Outer Side 27 Face Wall 28 Face Wall 29 Counterpart Surface A Envelope Circle B Envelope Circle 

1-8. (canceled)
 9. A switchable component for a valve drive of an internal combustion engine, comprising: a housing having a bore; an inner element, which has a cutout and an annular face, held in the bore of the housing having a head projecting beyond an edge of the housing; a lost motion spring, which is braced in the bore of the housing between the housing and the inner element forcing the housing and the inner element axially away from one another; at least one coupling piston seated in the cutout of the inner element and axially is moveable beyond an annular surface between the inner element and the housing and in sections, contacting a driver surface of the housing; and a locking ring or a locking ring pack having an inner shell and a circular-arc-shaped outer shell resting in an annular groove of the bore of the housing, and against an underside of the locking ring or the locking ring pack of, the inner element, in a deployed state, bears against the locking ring or the locking ring pack with the annular face such that a relative position is defined, wherein the locking ring or the locking ring pack, proceeding from a surface of at least one of the outer shell or the inner shell, has recesses which form lobe-like sections situated circumferentially in between the outer shell and the inner shell.
 10. The component as claimed in claim 9, wherein the locking ring or the locking ring pack has envelope circles and between the envelope circles, a ring is formed which two or more annular lugs formed with a substantially constant width.
 11. The component as claimed in claim 9, wherein the locking ring or the locking ring pack has envelope circles and between the envelope circles, a ring which has annular lugs and a greatest width in a section situated opposite the annular lugs with a width that decreases, as viewed from the section in a circumferential direction toward the annular lugs, at an inner envelope circle.
 12. The component as claimed in claim 9, wherein a coupling play is set between the locking ring or the locking ring pack and the inner ring by the locking ring or the locking ring pack.
 13. The component as claimed in claim 9, wherein when only one locking ring is used, the locking ring can have an assortment of thicknesses.
 14. The component as claimed in claim 9, wherein when the locking ring pack, which has two or more locking rings with lower locking rings and uppermost locking rings, is used, the lower locking rings have a of uniform thickness and the uppermost locking rings can have an assortment of thicknesses.
 15. The component as claimed in claim 9, wherein the inner shell of the locking ring or the locking ring pack has a bowstring-shaped flattening, which projects radially inward and the inner element has a longitudinal flattening on an outer shell surface which interacts with the bowstring-shaped flattening of the inner shell.
 16. The component as claimed in claim 9, wherein the housing has an aperture with face wall and the locking ring or the locking ring pack has annular lugs which are seated and bent radially outwards in the aperture of the housing and bear with water sides against the walls of the aperture such that the inner element is prevented from rotating relative to the housing.
 17. The component as claimed in claim 9, wherein the annular groove in the bore of the housing is located in a region near the edge of the housing.
 18. The component as claimed in claim 9, wherein the recesses, in conjunction with the lobe-like sections, generate a wave-like, tooth-like or box-like profile.
 19. The component as claimed in claim 9, wherein a flat or a cylindrical counterpart surface formed on an underside of the coupling piston, which is complementary to the driver surface.
 20. The component as claimed in claim 9, wherein the cutout is a radial bore in which two coupling pistons are situated diametrically opposite one another.
 21. The component as claimed in claim 9, wherein a flat or a cylindrical counterpart surface formed on an underside of the coupling piston, which is complementary to the driver surface.
 22. The component as claimed in claim 9, wherein the driver surface of the housing is a window, a bore, an annular groove, or an annular groove segment. 